Chromium (VI) ions react with diphenylcarbazide in weakly phosphoric solution. The product, diphenylcarbazone, is a red-violet complex which can be detected photometrically at 550 nm. The chromate cell test kit is suitable for the concentration range of 0.11 – 4.46 mg/L chromate allowing the concentration of chromium(VI) in a water sample to be determined without the use of a calibration curve by multiplying the measured absorbance at 550 nm with a known factor.